The context

Under her proposal, regulators would be appointed to undo some tech mergers. Her plan also calls for legislation that would prohibit platforms like Amazon from both offering a marketplace for commerce and participating in that marketplace.

Obstacles

The tech companies Ms. Warren has called out grew the way they did because, well, they wanted to. Officials at top tech companies have previously signaled that they believe they can police themselves, and they are highly unlikely to accept any sort of government regulation without a costly and bruising fight.

It is also unclear how popular Ms. Warren’s antitrust proposal is with voters, many of whom have come to enjoy and rely on the services offered by big tech.